<br>Dear QE USERS,<br><br>I am facing the following error  during polarisation computation with Berry Phase method;<br> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%<br>     from c_phase : error #         1<br>
     Polarization only for insulators and no empty bands<br> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%<br><br>     stopping ...<br><br>even though, I have fixed  the occupations which is needed for an insulator ?<br>
<br>Does this mean that Berry Phase calculation in QE is only for BAND-INSULATOR, and not for any <br>other insulator ? Does this mean, if one has odd number of electrons in a unit-cell, then QE can not <br>treat the system as insulator, even one forces QE to do so by specifying occupation "fixed" ?<br>
 <br>Looking forward to your kind reply.<br><br>Input files are appended below :<br> &control<br>    calculation  = 'scf'<br>    restart_mode = 'from_scratch'<br>    pseudo_dir   = '/home/pseudo/'<br>
    outdir       = './'<br>    tstress=.true.<br>    tprnfor=.true.<br> /<br> &system<br>    ibrav=1<br>    celldm(1)=6.84,<br>    nat=5<br>    ntyp=3<br>    ecutwfc=50.0,<br>    ecutrho=400.0,<br>    occupations='fixed'<br>
    tot_magnetization=3.0<br>    nspin=2,<br> /<br> &electrons<br>    conv_thr = 1e-7,<br> /<br>ATOMIC_SPECIES<br>   Bi   209.0      Bi.pbe-d-mt.UPF<br>   Fe    55.85     Fe.pbe-nd-rrkjus.UPF<br>   O     16.00     O.pbe-mt.UPF<br>
ATOMIC_POSITIONS<br>  Bi    0.000    0.000    0.010<br>  Fe    0.500    0.500    0.500<br>  O     0.000    0.500    0.500<br>  O     0.500    0.500    0.000<br>  O     0.500    0.000    0.500<br>K_POINTS {automatic}<br>  4 4 4 1 1 1<br>
<br>BerryPhase.in:<br><br> &control<br>    calculation   = 'nscf'<br>    pseudo_dir    = '/home/pseudo/'<br>    outdir        = './'<br>    lberry        = .true.<br>    gdir          = 3<br>    nppstr        = 7<br>
 /<br> &system<br>    ibrav         = 1<br>    celldm(1)     = 6.84<br>    nat           = 5<br>    ntyp          = 3<br>    ecutwfc       = 50.0<br>    ecutrho=400.0,<br>    tot_magnetization=3.0,<br>    nspin=2<br>    occupations='fixed'<br>
 /<br> &electrons<br> /<br> ATOMIC_SPECIES<br>   Bi   209.0      Bi.pbe-d-mt.UPF<br>   Fe    55.85     Fe.pbe-nd-rrkjus.UPF<br>   O     16.00     O.pbe-mt.UPF<br>ATOMIC_POSITIONS<br>  Bi    0.000    0.000    0.010<br>
  Fe    0.500    0.500    0.500<br>  O     0.000    0.500    0.500<br>  O     0.500    0.500    0.000<br>  O     0.500    0.000    0.500<br>K_POINTS {automatic}<br>  4 4 7  1 1 1<br><br>Thanking you and with my best regards,<br>
<br>Srijan Kumar<br>R&D Associate,<br>Indian Institute of Science, <br>India, 560012<br>